Photolysis and TiO2 photocatalysis of the pharmaceutical propranolol: Solar and artificial light

This study focuses on the removal of the pharmaceutical propranolol (PRO) by direct photolysis and TiO2 photocatalysis. Two different devices were employed, one at laboratory scale with artificial light (Xe-lamp) and the other one at pilot scale using solar irradiation. The solar plant was based on CPCs photoreactors. Solar radiation was quantified by a radiometer. To compare both devices, radiation was also measured using actinometries. PRO degradation and mineralization were assessed to establish the feasibility of both treatments. For direct photolysis, the influence of wavelength ranges was evaluated. In addition, reactors made with different materials (quartz and Duran) were also tested. Significant PRO degradation could be observed employing quartz reactors in both devices. PRO removal achieved after 240 min was 77% and 71% for the solar and the laboratory device, respectively. However, mineralization accomplished resulted to be negligible (7% and 2%). For photocatalysis, different TiO2 concentrations (0.1, 0.2, 0.4 g L-1) were tested. When 0.4 g L-1 was used, the best results could be observed in both installations. PRO degradation percentages achieved after 240 min were 81% at the solar plant and 94% at laboratory. Meanwhile, mineralization reached was 30% and 41% in solar plant and laboratory device respectively. In order to compare the different catalyst loads at the two devices, kinetics were evaluated as a function of time and energy involved. As TiO2 concentration increased, higher reaction rates were obtained in both devices. In general, the laboratory device gave rates 1.1-1.5 times higher than the solar installation. Biodegradability (BOD5/COD), oxidation (COD) and toxicity (algae Chlorella vulgaris) evolution during solar photocatalysis were followed. Biodegradability improved slightly from 0 to 0.06 after 270 min for the solar device, remaining non-biodegradable. Toxicity, measured in percentage of photosynthesis inhibition, decreased with treatment time. Oxidation of intermediates was observed, as COD underwent a reduction of 30% after 270 min. This article also provides a section comparing different techniques found in literature employed for PRO abatement. (c) 2012 Elsevier B.V. All rights reserved.